Author Topic: Piston Ring Gap ( something new )  (Read 1797 times)

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Faron

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Piston Ring Gap ( something new )
« on: December 29, 2024, 02:39:23 AM »
I'm sure everyone here is aware that we gap the second ring bigger than the top , But -- has anyone tried the bigger gap on the Top Oil Expander as discussed by a top Ring supplier podcast , and just for the record , I happened to see the Video right before I was scheduled to gap the rings on my current 671 Blown 390 Combo and I am very pleased with the results

Mr Woodys Garage

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Re: Piston Ring Gap ( something new )
« Reply #1 on: December 29, 2024, 12:24:58 PM »
That Is How We Gapped The Rings On My 428 Stroker Build. We're Never Too Old To Learn New Things. Many Things Have Changed In The Past 20 Years, Raising The Performance And Durability Bar Quite A Bit... Obviously, I Am Very Happy With The Results As Well. They Speak For Themselves.
« Last Edit: January 03, 2025, 06:05:27 PM by Mr Woodys Garage »

Barry_R

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Re: Piston Ring Gap ( something new )
« Reply #2 on: December 30, 2024, 07:26:29 AM »
Had that discussion with a successful Pro Stock builder many years ago.
Made sense then.
Probably still does now.

My427stang

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Re: Piston Ring Gap ( something new )
« Reply #3 on: December 30, 2024, 08:09:13 AM »
What is the reason?
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Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

ArtZarateJr

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Re: Piston Ring Gap ( something new )
« Reply #4 on: December 30, 2024, 09:00:33 AM »
Yes, and in one back to back test, the engine was able to carry power another 800rpm before slowly decreasing from max power. That was the major advantage I observed after changing the recommended gap of "minimum 0.015" to 0.035". This was actually larger than the second ring gap at 0.028".

ArtZarateJr

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Re: Piston Ring Gap ( something new )
« Reply #5 on: December 30, 2024, 09:06:41 AM »
What is the reason?

The reason is to vent any pressurized gasses, that pass the second ring, into the crankcase without restriction.

I run adjustable PCV valves from ME Wagner on all my builds, and I find they work great in this situation. No seal pushout or seepage anywhere. The valve covers are oil free at the breathers. On the FE I install the valve in the rear of the intake with a fabricated baffle beneath it. I run the line to a MOROSO catch can and back to the intake.

My427stang

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Re: Piston Ring Gap ( something new )
« Reply #6 on: December 30, 2024, 07:27:11 PM »
What is the reason?

The reason is to vent any pressurized gasses, that pass the second ring, into the crankcase without restriction.

I run adjustable PCV valves from ME Wagner on all my builds, and I find they work great in this situation. No seal pushout or seepage anywhere. The valve covers are oil free at the breathers. On the FE I install the valve in the rear of the intake with a fabricated baffle beneath it. I run the line to a MOROSO catch can and back to the intake.

But only the top of the two scrapers?
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Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

Mr Woodys Garage

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Re: Piston Ring Gap ( something new )
« Reply #7 on: December 30, 2024, 10:39:28 PM »
Yes

My427stang

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Re: Piston Ring Gap ( something new )
« Reply #8 on: December 31, 2024, 03:36:53 PM »
That's interesting, of course similar to the top and second ring relationship. 

I can see that if you are venting the second ring to make sure it doesn't flutter the first, you pay as well go one step deeper on the piston and dump in into the piston so it doesn't flutter the second.

However, I am very skeptical of it carrying more RPM because of that, especially 800 rpm.  I don't have anything without pistons in it, but may try it on a FAST build I have coming up.

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Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

Faron

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Re: Piston Ring Gap ( something new )
« Reply #9 on: January 01, 2025, 03:26:29 PM »
The reason as to why the top of the expander IS Oil Control , since the second is MOSTLY a scraper, The easier to get the oil into the oil grove the better , the gap is typically very tight on the expander rings not being able to handle the oil will unload the seal on the second and possibly the top as well , this was first tried on Blown Alcohol Combos , but seems to work on NA as well

CaptCobrajet

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Re: Piston Ring Gap ( something new )
« Reply #10 on: January 01, 2025, 04:12:59 PM »
Faron is correct.  The benefits of the wide gap on the top rail are more substantial if you use a tapered hook groove (Napier) second ring.  The piston scoops up oil like a parachute, and forces it through the oil ring expander to lubricate the cylinder wall.  The wiper ring peels that oil off the cylinder.  It needs to go somewhere.  The “drain” needs to be big enough to get rid of the oil.  It also helps to remove top ring leftovers that go through the second ring gap. 

I have been doing these things with rings for 20+ years.  Anything you can do to help the top ring do its job is a benefit. I guess it is more talked about these days.  I remember not too long ago a customer took one back apart and informed me that my second ring gaps were “way off”.  He just didn’t understand it was done on purpose.  Better ring seal can change where peaks occur, and also how well the engine can hold its head up after peak.
Blair Patrick